The invention pertains to mobile earth moving machines and more particularly to tractor scrapers with hydraulic controls raising and lowering the scraper bowl.
1. Field of the Invention
The raising and lowering of the scraper bowl is performed by a pair of hydraulic cylinders supporting the front of the bowl. The cylinder rods are extended to drop the bowl lowering the scraper blade into digging engagement with the ground or retracted to lift the bowl for hauling. When dumping, the bowl is partially lowered, the load is pushed out, and the dirt spread over the ground at a relatively uniform depth.
2. Description of the Prior Art
A control for operating the bowl cylinders will have a valve spool which is positioned to direct hydraulic fluid either to the rod ends of the cylinders for lifting the bowl or to the piston ends for lowering the bowl. A quick drop function can be provided as a separate lowering action by utilizing a separate valve spool and source of fluid under pressure which delivers an extra volume of hydraulic fluid to the cylinders causing them to rapidly extend when it is desired to lower the bowl quickly as may be the case when excavating between grade markers and stopping the machine each time to exactly position the blade would be too time consuming.